Habit differentiation and chromosome evolution inPleione (Orchidaceae)

Karyotypic and heterochromatin studies suggest a basic division of the orchid genusPleione into two groups, one represented by the clearly epiphytic species and the other including both species with terrestrial trends as well as those that are truly terrestrial. The epiphytic group possesses only (sub) metacentric chromosomes and is characterised by a considerable amount of terminal heterochromatin while the terrestrial group has some subtelocentric chromosomes and only small amounts of centromeric heterochromatin. It is concluded that a major phyletic split in the mode of chromosome change occurred during the transition from the epiphytic to the terrestrial habitat.